Because it seems utterly absurd. To know what the entire competitive Pokecommunity knows, what they're studied and tested, ya need t' put unsaved months into it. That's such an incredible waste of time, I simply can't see anyone doing that. Ever.

More importantly, you can't learn of the communities' processed data. All'a that raw information and facts learned isn't of much use 'til its form is shaped and numbers are crunched. Statistics, damage calcs, movepools, etc. aren't obtained by rhomping around in-game. Ya can't study a metagame without lookin' at the statistics a community like Smogon pools together. Ya can't learn quite a few important things without outright hackin' the game and digesting the coding int' somethin' useful. Even the world's most skilled competitive battler wouldn't be performing adequately without all'a that immensely important knowledge. Pokemon is a tactical game, information is just as valuable (and moreso at times) than raw intelligence.

Point being, it's outright impossible to be a great competitive battler with just the information someone has learned on their own.

In your opinion. . I once bought a pokedex from 4th gen and it said corsal was a fire flying type along with some other completly incorrect things, also i waste a lot of time with pointless stuff, I shit you not. ( e.g these conversations on the internet with pep that don't know me )I'll be back soon gotta go fin somethin.

It's a fact that you're playing with a cripple, that's somefin you'll have to accept. If you want to discover this stuff for yourself, so be it, but you can't be very serious about competitive Pokemon at the same time. Doing both at once doesn't work well, as Dirge said.

And regarding your distrust of outside sources, online Pokemon sources like Smogon, Bulbapedia, Serebii, Marriland, etc are usually correct. Obviously mistakes aren't unheard of, especially in a recently released generation, but you can check multiple sources. If you stumble upon an error and don't realize it, you're still wasting less time than if you were trying to find it all out yourself.

In a nutshell, don't try to be serious about being competitive and this "I'll figure it all out myself" mindset, when it comes to Pokemon.